Microwave irradiation for enhancing the regioselective synthesis of 6H-indolo[2,3-b]quinoxalines

Abstract

Microwave irradiation (MWI) promotes the regioselective synthesis of 6H-indolo[2,3-b]quinoxaline (5) by condensation of isatin (1) with o-phenylenediamine. Ethyl indolo[2,3-b]quinoxaline-6-acetate (8) was prepared via the carbethoxymethylation of 5, or from the reaction of N- (ethoxycarbonylmethyl)isatin (6) with o-phenylenediamine under MWI, The reaction of 8 with hydrazine hydrate afforded the hydrazide 9, whose condensation with aromatic aldehydes and monosaccharides gave the hydrazones 10a-d.